This invention relates generally to devices for setting off an explosive charge and more particularly to a chip slapper type detonator.
Chip slapper type detonators in general cause a xe2x80x9cflying platexe2x80x9d to be propelled at a high velocity against a secondary explosive medium creating a shock wave which results in the detonation of the secondary explosive. In a typical design, there are two wide area conductive lands separated by a narrow rectangular bridge member. The lands are connected to a capacitor through a high voltage switch. When the switch closes, the capacitor provides current across the lands which vaporizes the bridge member turning into a plasma. This plasma accelerates a portion of the dielectric material covering the bridge member to a high velocity, causing it to slap into an explosive. The resulting shock wave causes detonation of the explosive.
Traditional chip slappers include a ceramic substrate and a copper conductive layer on one surface of the substrate in the shape of the two wide lands separated by the narrow bridge portion. There may be a protective gold coating on the copper to prevent the copper conductive layer from corroding and to enhance electrical connections made to the lands. A flyer layer made of polyimide is then secured over the bridge portion.
There are several potential problems associated with this current design. First, the flyer layer does not exhibit an affinity for the gold coating and may not properly stick in place on the bridge portion. Second, the gold of the coating can migrate into the copper of the conductive layer and vice versa. The result is that the gold coating loses its corrosion prevention ability and its ability to enhance the electrical connections to the lands. Also, when the copper material migrates into the gold, there is a higher susceptibility to corrosion.
It is therefore an object of this invention to provide an improved chip slapper.
It is a further object of this invention to provide such an improved chip slapper in which the flyer layer is more easily and securely affixed over the bridge portion of the chip slapper.
It is a further object of this invention to provide such an improved chip slapper which prevents the gold of the protective coating for migrating into the copper of the conductive layer and vice versa.
It is a further object of this invention to provide such an improved chip slapper which is thus more resistant to corrosion.
It is a further object of this invention to provide such an improved chip slapper in which the gold coating retains its electrical connection enhancement ability.
It is a further object of this invention to remove the gold from the bridge area to improve the energy efficiency of the detonator.
The invention results from the realization that adding a buffer material between the gold coating and the conductive copper of the lands of the chip slapper prevents the gold from migrating into the copper and vice versa thus retaining the corrosion resistance properties of the gold and the electrical properties of the copper and from the further realization that if the gold coating is removed from the bridge portion of the copper between the lands, the exposed buffer material assists in adhering the flyer plate to the bridge portion, prevents the etchants used in the manufacturing process from adversely affecting the copper, and, in addition, less energy is required to make a plasma which accelerates a portion of the flyer layer (i.e., the xe2x80x9cflying platexe2x80x9d ) into an explosive. Thus, one of the advantages of the chip slapper design of the subject invention is that for a given energy input to the slapper, it is able to provide a larger shock wave to detonate the explosive and, conversely, less energy is required to provide the same shock wave to an explosive as a conventional bridge, and, as a result, smaller systems can be designed.
This invention features a chip slapper comprising a substrate; a sticking layer on the substrate; a conductive layer on the sticking layer in the shape of two lands separated by a bridge portion between the two lands; a buffer material on the conductive layer; a coating on the buffer layer extending across at least a substantial portion of the two lands but absent from the bridge portion; and a flyer layer over the bridge portion. The buffer material advantageously prevents migration of the material of the coating into the material of the conductive layer and vice versa and also better adheres the flyer layer on the bridge portion where the coating is absent.
The substrate is typically made of a ceramic material, the sticking layer may be made of a titanium-tungsten composition, the conductive layer is typically made of copper, the buffer material may also be made of a titanium-tungsten composition, the coating may be gold, and the flyer layer is typically a polyimide material. In the preferred embodiment, the material of sticking layer and the buffer material are the same. This invention also features a chip slapper with at least a substrate; a conductive layer on the substrate in the shape of two lands separated by a bridge portion between the two lands; a coating on the lands of the conductive layer but absent from the bridge portion; and a flyer layer over the bridge portion.
Further included may be a sticking layer on the substrate under the conductive layer to adhere the conductive layer to the substrate, and a buffer material between the coating and the conductive layer to prevent migration of the material of the coating into the material of the conductive layer and vice versa in the area of the lands. In the preferred embodiment, the buffer material extends across the bridge portion where the coating is absent to promote adhesion of the flyer layer to the bridge portion.
This invention also features a chip slapper with at least a substrate; a conductive layer on the substrate in the shape of two lands separated by a bridge portion between the two lands; a buffer material on at least the bridge portion of the conductive layer; and a flyer layer over the bridge portion such that the buffer layer promotes adhesion of the flyer layer to the conductive layer.
Further included may be a protective coating on the lands of the conductive layer to protect the conductive layer against corrosion in the area of the two lands but absent from the bridge portion to facilitate securing the flyer layer to the bridge portion. In the preferred embodiment, the buffer material extends between the conductive layer and the protective coating in the area of the lands to prevent migration of the material of the protective coating into the material of the conductive layer and vice versa. There may also be a sticking layer between the substrate and the conductive layer to promote adhesion between the conductive layer and the substrate.
One method of making the chip slapper of the subject invention is to deposit a sticking layer on a substrate, a conductive layer on the sticking layer, and depositing a buffer material on the conductive layer and to coat the conductive layer; then etch the sticking layer, the conductive layer, the buffer layer, and the coating into the shape of two lands separated by a bridge portion between the two lands; remove the coating from the bridge portion to reveal the buffer material; and then attach a flyer layer to the bridge portion.